JPS647113A - Temperature controller - Google Patents

Abstract

PURPOSE:To improve the safety by providing a detecting means which detects not only the change of the temperature resistance of an electrode wire but also the potential difference between both ends of the electrode wire. CONSTITUTION:A temperature control circuit consists of an electrode wire 2 which has a one-body constitution and has the resistance value changed by temperature, a heater wire 3, a resin 4 whose impedance is changed by temperature, a power control means 5, a constant current circuit 6, a first heating resistance 7, a detecting means 8, a smoothing circuit 9, a temperature setting means 10, a control means 11, a power supply circuit 12 and a safety circuit 16. Since the current leaked from the resin 4 is increased at the time of local warming, the potential difference between both ends of the electrode wire at this time is larger than that at the time of normal temperature control to reduce the surface temperature of an electric carpet. Normally, the safety circuit 16 is not operated because the current flowing to the heating resistance is small.